1. Field of Invention
This invention relates to a slideable cylindrical valve for controlling the hydrogen flow in fuel cell.
2. Background
Fuel cells, such as PEM fuel cells, use a simple chemical reaction to combine hydrogen and oxygen into water, producing electric current in the process. Hydrogen may be produced by a chemical reaction between a fuel, such as lithium aluminum hydride, and water vapor or by absorption/desorption-adsorption/desorption of hydrogen from a metal hydride. At an anode, hydrogen molecules are ionized by a platinum catalyst, and give up electrons. The proton exchange membrane (PEM) allows protons but not electrons to flow through the membrane. As a result, hydrogen ions flow through the PEM to a cathode, while electrons flow through an external circuit. As the electrons travel through the external circuit, they can perform useful work by powering an electrical device such as an electric motor, light bulb or electronic circuitry. At the cathode, the electrons and hydrogen ions combine with oxygen to form water. The byproducts of the reaction are water and heat.
Valves currently suitable for controlling hydrogen flow in passively regulated micro fuel cells require high tolerances to provide adequate sealing, yet need to be capable of allowing transport of sufficient hydrogen to respond to the demand of the electrical load. High tolerance valves meeting these requirements are difficult to manufacture, expensive, and often require high actuation force.